The researchers studied a group of overweight males. The volunteers walked for 60 minutes at 60% maximum oxygen consumption on an empty stomach and, on another occasion, two hours after consuming a high-calorie carbohydrate-rich breakfast. The research team took multiple blood samples after eating or fasting and after exercising. The researchers also collected adipose tissue samples immediately before and one hour after walking.
Gene expression in the adipose tissue differed significantly in the two trials. The expression of two genes, PDK4 and HSL, increased when the men fasted and exercised and decreased when they ate before exercising. The rise in PDK4 likely indicates that stored fat was used to fuel metabolism during exercise instead of carbohydrates from the recent meal. HSL typically increases when adipose tissue uses stored energy to support increased activity, such as during exercise, explained Dylan Thompson, corresponding author of the study.
These results reinforce the view that "adipose tissue often faces competing challenges," Thompson wrote. After eating, adipose tissue "is busy responding to the meal and a bout of exercise at this time will not stimulate the same (beneficial) changes in adipose tissue. This means that exercise in a fasted state might provoke more favorable changes in adipose tissue, and this could be beneficial for health in the long term," he noted.
Abstract
Feeding profoundly affects metabolic responses to exercise in various tissues but the effect of feeding status on human adipose tissue responses to exercise has never been studied. Ten healthy overweight men aged 26 ± 5 years (mean ± SD) with a waist circumference of 105 ± 10 cm walked at 60% of maximum oxygen uptake under either FASTED or FED conditions in a randomised, counterbalanced design. Feeding comprised 648 ± 115 kcal 2 h before exercise. Blood samples were collected at regular intervals to examine changes in metabolic parameters and adipokine concentrations. Adipose tissue samples were obtained at baseline and one hour post-exercise to examine changes in adipose tissue mRNA expression and secretion of selected adipokines ex-vivo. Adipose tissue mRNA expression of PDK4, ATGL, HSL, FAT/CD36, GLUT4 and IRS2 in response to exercise were lower in FED compared to FASTED conditions (all p ≤ 0.05). Post-exercise adipose IRS2 protein was affected by feeding (p ≤ 0.05), but Akt2, AMPK, IRS1, GLUT4, PDK4 and HSL protein levels were not different. Feeding status did not impact serum and ex-vivo adipose secretion of IL-6, leptin or adiponectin in response to exercise. This is the first study to show that feeding prior to acute exercise affects post-exercise adipose tissue gene expression and we propose that feeding is likely to blunt long-term adipose tissue adaptation to regular exercise.
Authors
Yung-Chih Chen, Rebecca L Travers, Jean-Philippe Walhin, Javier T Gonzalez, Francoise Koumanov, James A Betts, Dylan Thompson
[link url="https://www.sciencedaily.com/releases/2017/04/170406152651.htm"]American Physiological Society material[/link]
[link url="http://ajpendo.physiology.org/content/early/2017/03/08/ajpendo.00006.2017"]American Journal of Physiology – Endocrinology and Metabolism abstract[/link]